Today, the parts of the vehicle body are continuously configured so that the junctions of the parts would not outstand. For example, the bumper of the vehicle is designed to be continuous with an adjacent vehicle body panel. Furthermore, the edges of the bumper are required to appear combined with the adjacent vehicle body panel.
Generally, the resin molded articles are used for bumpers of mass-produced vehicles to reduce cost and to cope with various designs.
However, the shapes of the bumpers are decided based on the above-mentioned requirement. So, the resin molded articles for the bumpers often have undercut portions. The undercut portions are extended to the traverse direction with respect to the releasing direction of the metal mold, which shapes the resin molded articles.
Conventionally, JPA-H10-71634 discloses the metal mold for production of molded articles having undercut portions. The metal mold comprises a first die, a first slide core, a second slide core and a second die. The first die forms the outer surface of the body portion of the molded article and one part of the outer surface of the undercut portion. The first slide core forms the rest of the outer surface of the undercut portion. The second slide core forms the inner surface of the undercut portion and one part of the inner surface of the body portion. The second die forms the rest of the inner surface of the body portion.
Regarding the metal mold disclosed in JPA-H10-71634, the first slide core and second slide core can move independently in the different direction from the operation direction of the first die against the second die. In opening the metal mold, the first slide core moves in the removal direction of the undercut portion and then both of the first and second slide cores move integrally in the removal direction.
As shown in FIG. 12(a), first, compound, such as resin composition or the like, is shot into the cavity of the metal mold and a molded article 120 is molded, which has an undercut portion 122. Second, a first slide core 111 is actuated by a cylinder to the first direction (rightward in FIG. 12), which is different from the operation direction of the first die against the second die 103 (the vertical direction in FIG. 12). Third, the first slide core 111 contacts a stopper 131 fixed to the second slide core 112 (shown in FIG. 12(b)), and then the first slide core 111 and second slide core 112 move rightward integrally (shown in FIG. 12(c)). Finally, the undercut portion 122 is removed from a movable die 113.
Then, as shown in FIG. 12(d), the molded article 120 is removed by pulling in the opening direction of the first die (upward in FIG. 12). After removing the molded article 120, the cylinder is elongated (shown in FIG. 12(e)) and the first slide core 111 and second slide core 112 are shifted to each initial position (shown in FIG. 12(f)).